Process of making fertilizers.



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SPENCER B. NEWER-BY AND Iii. BARRETT, 0F BAYBRIDGE, 0E0.

PROCESS OF G- lEEETEIZERS.

No Drawing.

To all whom it may concern."

Be it known that we, SPENCER BpNnW- BERRY and HARVEY N. BAnRET'r, citizens of the United States, residing atBaybridge, in the county of Erie and State of Ohio, have invented a certain new and useful Improvement in Processes of Making- Ferti lizers, of which the following is a specification.

Our invention relates to the making of citrate soluble phosphatic fertilizer from natural phosphates by heating the natural phosphates with a relatively small amount of alkali metal bisulfate. By natural phosphate we mean phosphate rock, consisting of phosphate of lime or phosphate of alu mina and iron, apatite, phosphorite, guano, phosphate, or other forms of mineral phoric acid is in a form substantially insoluble in ammomum cltrate solution and unavailable, in an untreated condition, for

. use as fertilizer.

The amount of alkali metal bisulfate required to eifect the conversion of the natural phosphate to citrate-soluble condition varies with the purity of the phosphate to be treated, but in the case of sodium bisul fate, Na SO may be generally stated to be an amount of anhydrous bisulfate equal to from one-sixth to two-thirds the phosphoric acid contained inthe phosphate. If potassium bisulfate is used, the quantity required is greater than that .of bisulfate of soda in the proportion of the equivalent or molecular weights of the two substances, 142 parts by weight of anhydrous sodium bisulfate being equivalent to 17 4 parts of potassium bisulfate. .A natural phpsphate containing 30 per cent. of phosphoric acid, P 0 will therefore require the addltion of approximately five to twenty per cent. by weight of anhydrous sodium bisulfate, or six to twenty-four per cent. of potassium bisulfate. We do not wish, however, to be limited to these precise proportions, as good results may be obtained by the use of greater or less amounts of alkali metal bisulfatethan those stated. An excess of sulfate is not objectionable, except in respect to unnecessary cost, while by employing very high or long-continued heat a good result may be obtained by the use; of-

even a less amount of alkali metal bisulfat than the minimum above stated.

In preparing the mixture of phosphate Specification of Letters Patent.

Application filed March 15, 1912. Serial No. 684,013.

- ing heat, attain' Patented Feb. 29, 31%116.

bisulfate are ground together, wet or dry, or separately ground and then mixed, or the bisulfate is dissolved in water and the solution mixed with the ground phosphate.

The process of calcination is conducted in such manner that the mixture is gradually raised to an orange or white heat, in an oxidizing atmosphere, and maintained at and alkali metal, the natural phosphate and high temperature,- until the sulfuric acid of the bisulfate is practically all expelled as sulfur dioxid and oxygen, which escape with the products of combustion, leaving the calcined product substantially free from sulfates. This liberation of gaseous products has the effect of making the calcined product exceedingly porous and soft, and promotes its solubility. The temperature required varies inversely with the amount of sulfate used, but is generally fi-om 2500 to 2800 F. It is important that during the heating the materlal shall be continually agitated or turned over to present fresh surfaces to the oxidizing heat. The simplest and most effective apparatus for the production of the conditions described is an internally-fired revolving kiln, as used in making Portland cement, although kilns or furnaces of other types may also be used.

As a practical example of the working of our process, we take ordinary phosphatethe kiln, to a constantly increasing oxidiz a maximum of probably 2500 to 2800 F. The charge is maintained at maximum heat from one-half to one hour, and is continually discharged in the form of soft, porous clinkers. The product is cooled and ground to powder, and is then found to be practically entirely citrate-soluble, and suitable for use as fertilizer or as an ingredient of commercial fertilizers. The first part of this process when applied strictly to bisulfates would require a change in the proportions of those stated above. In thus working our process we take ordinary phosphate rock, and add from nine to thirtyfour per cent. of anhydrous bisulfate of soda, or from ten to forty per cent. of bisulfate of potash, and grind. to powder, and then proceed. as stated above.

The use of bisulfate of potash has an advantage over that of bisulfate of soda in that the potash contained in the product has in itself a great fertilizing effect, and the commercial value of the product is thereby increased. Owing to the higher cost and greater volatility of potash, however, as compared with soda, it is advisable, when potassium bisulfate is used, to provide suitable appliances for prevention of loss of alkali, such as dust chambers back of the kiln and water-spray in the stack.

The temperature required is such as will evolve sulfur dioxid from the mixture and the period of high heat is such as will drive off substantially all the sulfur dioxid and the temperatures and times above indicated furnish a good illustration of what is required.

The mixture is such and the temperature and period of heating are such that the product, when the process is finished, will not be water soluble, but will be citrate soluble. So far as our process in its preferred form is concerned, {the result isreached solely by the presence of the bisulfate in the mixture and the action of heat thereon, and not by the assistance of other re-agents, though such might be present without materially detracting from the process here sought to be covered. Obviously, there can be considerable variation in the temperature and time and quality and quantity of reagent without departing from the spirit of our invention.

While the percentage and proportion of sodium or potassium bisulfate introduced will depend upon the amount of phosphoric acid present and will therefore be variable, still for the purposes of a concrete illustration it may be said that where the natural phosphate contains 30% of phosphoric acid, there should be added to it from to approximately 300 pounds of sodium carbonate for each. 1400 pounds of phosphatio material 'or from approximately 100 to 350 pounds of potassium bisulfate to each 1400 pounds of phosphatic material. In practice the material is first reduced to a powder substantially such as would pass through a sieve of 60 meshes and when water is used the quantity is substantially such as would reduce the product/to a kind of mud. The temperature is gradually increased from a relatively low degree to approximately 2800 degrees. Beyond that the difficulties of maintaining the temperature are very great and there is no material advantage.

We claim;

1. The process of making fertilizer by heating an intimate pulverized mixture of natural phosphate with from five to twentyfour per cent. of alkali metal bisulfate, in an oxidizing atmosphere, at a temperature of 2500 F. to 2800 F., until the alkali metal bisulfate is substantially decomposed with liberation of sulfur dioxid and oxygen, and

the natural phosphate is rendered substanheating for from 20 minutes to an hour and ten' minutes, until approximately all the sulfur dioxid is driven off and the residuum rendered citrate-soluble but non-soluble in Water. a

4. The process of producing a citrate soluble fertilizer which consists in mixing natural phosphate with not more than approximately 25% of alkali-metal bisulfate, heating the mixture to from 2500 to 2800 Fahrenheit until the bisulfate is substantially decomposed, continuing the heating until approximately all'the sulfur dioxid is driven off and the residuum rendered citrate soluble but non-soluble in water.

5. The process of producing a citrate soluble fertilizer, which consists in mixing natural phosphate with less than 25% of alkali-metal bisulfate, hcatingthe mixtureto approximately 2500 to 2800 Fahrenheit until the bisulfate is substantially decomposed and continuing the heating for from 20 minutes to an hour and ten minutes or until approximately all the sulfur dioxid is driven off and .the residuum rendered citrate soluble but non-soluble in water.

6. The process of producing a citrate soluble fertilizer which consists in mixing natural phosphate with alkali-metal bisulfate, heating the mixture to approximately from 2500 to 2800 Fahrenheit until the bisulfate is substantially decomposed and continuing the heating for from 20 minutes to an hour and ten minutes or until approximately all the sulfur dioxid is driven off and the residuum rendered citrate soluble but non-soluble in water.

7. The process of making fertilizer by heating natural phosphate with alkali-metal bisulfates in such manner that the bisulfates are substantially decomposed with evolution of sulfur dioxid and the natural phosphate changed to citrate-soluble form.

8. The process of making fertilizer by heating natural phosphate with acid sulfates in such manner that the sulfates are substantially decomposed with evolution of sulfur dioxid and the natural phosphate changed to citrate-soluble form.

9. The process of making fertilizer .by heating natural phosphate with a small percentage of alkali-metal bisulfate until the bisulfate is substantially decomposed with evolution of sulfur dioxid and the natural phosphate changed to citrate-soluble form;

10. The process of making fertilizer by heating natural phosphate with a small percentage of acid sulfate until the sulfate is substantially decomposed with evolution of sulfur dioxid and the natural phosphatechanged to citrate-soluble form.

11. The process of making fertilizer by calcining phosphate with a small percentage of alkali-metal bisulfate, at nearly white heat until the bisulfate is substantially decomposed with evolution of sulfur dioXid and the natural phosphate changed to citrate-soluble form.

12. The process of maln'ng fertilizer by calcining phosphate with a small percentage of acid sulfate, at nearly white heat until the sulfate is substantially decomposed with evolution of sulfur dioxid and the natural phosphate changed to citrate-soluble form.

SPENCER B. NEERRY.

HARVEY N. BARRETT.

Witnesses:

'HATTIE M. MEGGITT,

TRVIN H. NU'BER. 

